Towards the industrialization of bio-inspired multiscale and hierarchical carbon fibre-reinforced polymer composites

Abstract

Carbon fibre-reinforced polymers (CFRPs) are widely used in the aerospace industry because of their outstanding strength-to-weight ratios. They present for their high strength, high stiffness, and low density. Nevertheless, due to the relatively weak interlaminar region of the laminated structure, these materials present poor mechanical properties in the direction perpendicular to the fibres, leading to catastrophic failure and delamination. Biomimetics has arisen as an interesting approach to improve damage tolerance of CFRPs. Among the different biological materials, nacre stands out due to its toughness and strength balance. The reason behind the nacre’s mechanical performance is its hierarchical and multiscale discontinuous staggered structure (known as ‘brick-and-mortar’). In this work two biomimetics approaches are implemented into CFRP composites. First, the introduction of a ‘brick-and-mortar’ structure by performing specific cuts into the prepregs forming the composites, resulting in “hierarchical CFRPs”. Second, the introduction an additional scale by the addition of nanoreinforcements (graphene-related materials, GRMs), producing “multiscale CFRPs”. Finally, “hierarchical and multiscale CFRPs” were developed by the combination of both approaches. In order to evaluate the potential applicability and scalability of such structures, the bio-inspired composites have been developed using manufacturing procedures and equipment already existing in the industry and with commercial materials. An evaluation of such manufacturing processes is presented in this work. For the “hierarchical CFRPs” the influence of the ‘brick-and-mortar’ structure in the mechanical performance of the composites has been investigated in terms of fracture toughness and behaviour under tensile loading. Similarly, for the “multiscale CFRPs” it has been studied the influence of the addition of GRMs on its physical-chemical and mechanical properties. Finally, the combination of both strategies was evaluated for the “hierarchical and multiscale CFRPs”. An enhancement in the fracture toughness and a change in the fracture behaviour of composites was obtained by implementing such strategies.